interval: Utilities for creation and manipulation of `Interval` objects

Description

interval() creates an Interval object with the specified start and end dates. If the start date occurs before the end date, the interval will be positive. Otherwise, it will be negative. Character vectors in ISO 8601 format are supported from v1.7.2.

int_start()/int_end() and int_start<-()/int_end<-() are "accessors" and "setters" respectively of the start/end date of an interval.

int_flip() reverses the order of the start date and end date in an interval. The new interval takes place during the same timespan as the original interval, but has the opposite direction.

int_shift() shifts the start and end dates of an interval up or down the timeline by a specified amount. Note that this may change the exact length of the interval if the interval is shifted by a Period object. Intervals shifted by a Duration or difftime object will retain their exact length in seconds.

int_overlaps() tests if two intervals overlap.

int_standardize() ensures all intervals in an interval object are positive. If an interval is not positive, flip it so that it retains its endpoints but becomes positive.

int_aligns() tests if two intervals share an endpoint. The direction of each interval is ignored. int_align tests whether the earliest or latest moments of each interval occur at the same time.

int_diff() returns the intervals that occur between the elements of a vector of date-times. int_diff() is similar to the POSIXt and Date methods of diff(), but returns an Interval object instead of a difftime object.

Usage

interval(start = NULL, end = NULL, tzone = tz(start))
start %--% end
is.interval(x)
int_start(int)
int_start(int) <- value
int_end(int)
int_end(int) <- value
int_length(int)
int_flip(int)
int_shift(int, by)
int_overlaps(int1, int2)
int_standardize(int)
int_aligns(int1, int2)
int_diff(times)

Value

interval() -- Interval object.

int_start() and int_end() return a POSIXct date object when used as an accessor. Nothing when used as a setter.

int_length() -- numeric length of the interval in seconds. A negative number connotes a negative interval.

int_flip() -- flipped interval object

int_shift() -- an Interval object

int_overlaps() -- logical, TRUE if int1 and int2 overlap by at least one second. FALSE otherwise

int_aligns() -- logical, TRUE if int1 and int2 begin or end on the same moment. FALSE otherwise

int_diff() -- interval object that contains the n-1 intervals between the n date-time in times

Arguments

start, end: POSIXt, Date or a character vectors. When start is a character vector and end is NULL, ISO 8601 specification is assumed but with much more permissive lubridate style parsing both for dates and periods (see examples).
tzone: a recognized timezone to display the interval in
x: an R object
int: an interval object
value: interval's start/end to be assigned to int
by: A period or duration object to shift by (for int_shift)
int1: an Interval object (for int_overlaps(), int_aligns())
int2: an Interval object (for int_overlaps(), int_aligns())
times: A vector of POSIXct, POSIXlt or Date class date-times (for int_diff())

Details

Intervals are time spans bound by two real date-times. Intervals can be accurately converted to either period or duration objects using as.period(), as.duration(). Since an interval is anchored to a fixed history of time, both the exact number of seconds that passed and the number of variable length time units that occurred during the interval can be calculated.

Examples

Run this code

interval(ymd(20090201), ymd(20090101))

date1 <- ymd_hms("2009-03-08 01:59:59")
date2 <- ymd_hms("2000-02-29 12:00:00")
interval(date2, date1)
interval(date1, date2)
span <- interval(ymd(20090101), ymd(20090201))

### ISO Intervals

interval("2007-03-01T13:00:00Z/2008-05-11T15:30:00Z")
interval("2007-03-01T13:00:00Z/P1Y2M10DT2H30M")
interval("P1Y2M10DT2H30M/2008-05-11T15:30:00Z")
interval("2008-05-11/P2H30M")

### More permissive parsing (as long as there are no intermittent / characters)
interval("2008 05 11/P2hours 30minutes")
interval("08 05 11/P 2h 30m")

is.interval(period(months = 1, days = 15)) # FALSE
is.interval(interval(ymd(20090801), ymd(20090809))) # TRUE
int <- interval(ymd("2001-01-01"), ymd("2002-01-01"))
int_start(int)
int_start(int) <- ymd("2001-06-01")
int

int <- interval(ymd("2001-01-01"), ymd("2002-01-01"))
int_end(int)
int_end(int) <- ymd("2002-06-01")
int
int <- interval(ymd("2001-01-01"), ymd("2002-01-01"))
int_length(int)
int <- interval(ymd("2001-01-01"), ymd("2002-01-01"))
int_flip(int)
int <- interval(ymd("2001-01-01"), ymd("2002-01-01"))
int_shift(int, duration(days = 11))
int_shift(int, duration(hours = -1))
int1 <- interval(ymd("2001-01-01"), ymd("2002-01-01"))
int2 <- interval(ymd("2001-06-01"), ymd("2002-06-01"))
int3 <- interval(ymd("2003-01-01"), ymd("2004-01-01"))

int_overlaps(int1, int2) # TRUE
int_overlaps(int1, int3) # FALSE
int <- interval(ymd("2002-01-01"), ymd("2001-01-01"))
int_standardize(int)
int1 <- interval(ymd("2001-01-01"), ymd("2002-01-01"))
int2 <- interval(ymd("2001-06-01"), ymd("2002-01-01"))
int3 <- interval(ymd("2003-01-01"), ymd("2004-01-01"))

int_aligns(int1, int2) # TRUE
int_aligns(int1, int3) # FALSE
dates <- now() + days(1:10)
int_diff(dates)